The present invention generally relates to trailer hitches of the type commonly used to connect a towing vehicle to a trailer and, more particularly, to a ball hitch assembly having a removable and easily interchangeable ball including structure for preventing the inadvertent disassembly of the hitch.
Trailer hitches are devices which connect a tow vehicle to a trailer by means of a ball hitch which is mounted onto the vehicle, or onto a tow bar which is connected to the vehicle. The hitch then mates with a socket located on the trailer tongue. This ball and socket configuration is designed to allow adequate rotation of the socket with respect to the ball so that the vehicle-trailer combination can maneuver around corners. Typically the socket mechanism has a releasably lockable coupling so that it locks onto the ball hitch to prevent decoupling while towing.
There are several standardized sizes of these ball and socket systems, the specific size usually depends on the size of the trailer or its weight and is specified by the outer diameter of the hitch ball. Typical ball sizes are diameters of 1-xe2x85x9e inches, 2 inches, 2-xc2xc inches, and 2-{fraction (5/16)} inches. For a trailer hitch to function properly and safely, it is important that the size of the ball matches that required by the particular hitch socket. Using a ball that is smaller than the size specified for the trailer could have disastrous consequences, and coupling a trailer with a ball that is too large for its socket is impossible. A vehicle may need to tow a variety of trailers, with sockets of different sizes, and hence there is a need to be able to employ different sizes of hitch balls on a vehicle.
Conventional hitch balls consist of a mounting bolt and ball as an integral unit. The unit is bolted onto the tow bar and requires at least one wrench for its removal and installation. This can be inconvenient because it requires that one carry the proper tools in the vehicle, as well as a variety of hitch balls, which can have their threads damaged if not properly stored. Additionally, the hitch ball mounting threads may become corroded or filled with debris so that removing the ball can be a formidable task, especially when trying to change a hitch ball at night in the rain. It is usually not feasible to have multiple, different-sized balls bolted to a vehicle because the ball must be located along the centerline of the vehicle and at a preferred height in order to evenly distribute the loads acting on the vehicle and trailer.
With the purpose of overcoming these problems, several types of hitches, which present other schemes of interchanging balls, have been invented. For example, U.S Pat. No. 4,433,854 issued Feb. 28, 1984 to Smith shows an interchangeable ball hitch in which the ball contains a spring-biased latch that locks the ball onto a mounting piece which is attached to the tow bar and which can be released for interchanging the ball sizes. The latch includes a spring and pin which are integral to the mounting piece. This device requires that the ball be rotated into the proper position for removal which can be difficult if trying to change a ball at night without a flashlight.
U.S. Pat. No. 5,169,168 issued Dec. 8, 1992 to Harry et al describes a hitch ball assembly including interchangeable balls and a mounting post which is attached to the tow bar. The mounting post contains a grooved path and the ball has a pin on the inner cavity of the ball. To mount the ball one must align the pin with the beginning of the groove at the top of the post and then rotate and depress the ball to move the pin along the groove until it has fully seated. Once seated, the ball is free to rotate around the mounting post. The pin can be damaged during towing by the trailer loads if the tolerances of the fit between the ball and post are too large or if the ball binds up in the hitch socket and then applies those extra loads to the post. In these instances a large portion of the trailer forces are being transferred to the vehicle through just the pin.
U.S Pat. No. 5,419,576 issued May 30, 1995 to Van Vleet, describes an interchangeable ball hitch connector which includes an interchangeable ball and a mounting post which is bolted onto the tow bar. The ball has a chamber which the mounting post fits within. Both the ball and the post have holes which are aligned when the ball is in place and through which a locking pin is placed to hold the two parts together.
U.S. Pat. No. 5,871,222 issued Feb. 16, 1999 to Webb describes a detachable ball hitch apparatus which includes a ball hitch with an integral post that fits into the cavity of a piece that mounts onto the tow bar. The post has a spring-loaded pin that slides into a groove in the tow bar piece. When the ball is fully mounted the pin is depressed to lock it into the groove to prevent its unintentional removal. Once installed, the ball is not free to rotate. If the spring should fail, the ball cannot be easily removed from the tow bar. Also, the pin and spring are located inside of the ball so this device would be more expensive than others because each of the interchangeable balls must contain those pieces.
While the above-described structures teach the use of detachable and/or interchangeable hitch balls for towing applications, there remains a need for improved interchangeable hitch ball assemblies. This need manifests in both the need for simplified structures as well as structures that can be manufactured efficiently at a reduced cost. The present invention is directed to providing an improved construction for interchangeable hitch ball systems.
It is the object of the present invention to provide for an improved tow hitch which includes an easily interchangeable hitch ball and which mates with standard hitch ball sockets.
It is another object of the present invention to provide a new and useful hitch ball and mounting structure that allows easy interchange of hitch balls of various sizes for different towing applications. A further object of the present invention is to provide an interchangeable hitch ball assembly that is easy to manufacture yet which is durable in use.
Still a further object of the present invention which provides for interchangeable hitch balls that can be release and relocked yet readily removed from a tow bar.
Yet a further object of the present invention is to provide a new and useful method for attaching an interchangeable hitch ball element to a mounting element in a towing application.
According to the present invention, then, an interchangeable hitch ball assembly for towing a trailer is provided. The hitch ball assembly generally includes a mounting element that is adapted to be secured to a vehicle and a hitch ball element that is adapted to be secured to the mounting element to define an assembled state. One of the mounting element and the hitch ball element includes a post while the other of the mounting element and the hitch ball element has a cavity formed therein such that the cavity has a threaded entryway and an interior chamber. The post has a threaded head portion with a selected axial head length. The interior chamber is then formed to have a depth greater than the axial head length of the head portion. The threaded head portion of the post may be threadably engaged by the threaded entryway but, the chamber and the entry way are dimensioned such that, when in the assembled state, the head portion resides in the interior chamber. This allows the hitch ball element and the mounting element to be freely rotatable with respect to one another, yet they are prevented from being disassembled from one another by drawing the hitch ball element axially away from the mounting element.
The mounting element is shown to include a base and means for securing the base to the vehicle, such as by a mounting shank. When the post is supposed on the base and the chamber is formed in the hitch ball element, this mounting shank extends co-axially of the post and oppositely thereof. The mounting shank then receives a fastener, such as a nut, to secure the base to the vehicle, such as the tow bar.
When the cavity is formed in the hitch ball element, this cavity is a bore that extends partway through the hitch ball element. The hitch ball itself may include solid geometric construction selected from a group consisting of spheres, cylinders, prisms, pyramids and cones. Where the hitch ball element is spherical, the chamber extends radially thereof.
An auxiliary interlock structure may be associated with the mounting element in the post and the hitch ball element. The auxiliary locking structure is adapted to selectively and releasively prevent disassembly of the hitch ball element from the post. In one embodiment, the auxiliary interlock structure is a spring clip that extends through bores formed in the mounting element which engage a groove on the mounting post. In another embodiment, the interlock structure is formed as a rotatable pin that has a cam structure and that is received within a groove on a portion of the hitch ball element. This pin can rotate between an open position wherein a cut-out portion provides clearance so that the hitch ball may be removed from the mounting post yet may be pivoted into a lock state wherein a cammed portion of the pin resides in the groove and therefore prevents disassembly of the hitch ball and mounting element.
In the exemplary embodiment, the axial head length of the threaded head portion of the post is length a1 and the entryway has an axial length a3. The unthreaded interior of the chamber has an axial length a4 and the post includes an unthreaded portion with an axial length a2. In such case, Axial length a4 is greater than axial length a1, and axial length a2 is greater than axial length a3. In addition, the post may include a pilot portion with an axial length a5. Here, the chamber includes a recess of axial length a6 wherein the axial a5 is greater than the axial length a6.
If desired, the hitch ball element may include a collar. In such event, the mounting element includes a recess such that the collar and the recess are dimensioned such that the collar resides in the recess when the hitch ball assembly is in the assembled state.
The present invention is also directed to a method of attaching interchangeable hitch ball element to a mounting element. This method can include any of the mounting steps inherent in the above described structure. Particularly, however, the method of the present invention includes inserting a threaded head portion of a mounting element into a threaded entryway of a cavity provided in the hitch ball and rotating the hitch ball element with respect to the mounting element in a direction to engage the threads at the entryway with the threads provided in mounting element. Further rotation of the hitch ball element with respect to the mounting element moves the threads of the mounting post beyond the entryway threads and into an unthreaded interior chamber. Thereafter, the method includes the step of allowing free rotation of the hitch ball element on the mounting element while the head portion is located within the chamber.
The method of the present invention can further include the steps of advancing the hitch ball element axially away from the mounting element and rotating the hitch ball element with respect to the mounting element in the direction to engage the threads on the head portion of the mounting element with the threads on the entry way of the cavity. Further rotation has been undertaken so that the threads of the head portion are disengaged from the threads of the entryway.